Technical Field
This disclosure relates generally to capturing images, and, more specifically, to compensating for aberrations in ambient lighting at the time of image capture.
Description of the Related Art
Image capture devices can suffer from poor performance when they are asked to capture high quality images across a wide variety of environments. For example, image capture devices have a relatively small number of features to call upon in order to affect the lighting of objects in the field of view. Generally, some sort of light source, such as a flash bulb or light-emitting diode (LED), or some other sort of lamp may be provided with portable image capture devices such that the devices can add lighting to the scene being captured.
However, some scenes that have sufficient lighting may suffer from ambient lighting with characteristics that may be detrimental to providing high-quality, visually appealing images. Under such circumstances, adding additional light from a devices LED flash unit may cause overexposure or may otherwise add to the detrimental characteristics of the ambient light (e.g., saturation in high illumination).
For example, some sources of indoor ambient light, such as fluorescent light bulbs have the illuminations characteristic of flickering on and of (e.g., at about 60 Hz AC). Fluorescent lamps may also have spectral roll. LED and other light sources may modulate at different frequencies (e.g., 100 Hz-2 KHz or higher) for example. Such on/off behavior may adversely affect the captures of images. Short camera exposures do not integrate sufficient time to low pass filter the ambient light and rolling shutter exposure mode causes exposure “beats” with illumination frequency. In some systems, a camera may be synchronized with the frequency of the AC electrical source that provides the ambient light. However, the frequency of the AC electrical source is not readily available to portable devices. In other systems, the captured image may be analyzed to determine the frequency and the exposure of subsequent images may be limited to a multiple of the period of the frequency. However, such a method is not helpful for preventing artifacts in the analyzed image and such a method requires analysis and sampling by the main CPU or detects ambient light in the front of the devices when the rear camera is in use.